1. Field of the Invention
The present disclosure relates to enabling media bypass of one or more session border controllers (SBCs) in a telecommunications network. In particular, but not exclusively, the present disclosure relates to enabling media bypass of one or more SBCs in a telecommunications network which includes a plurality of SBCs via which setup of a media session between endpoint devices can be established.
2. Description of the Related Technology
Packet-based telecommunications networks typically include session border controller (SBC) devices. An SBC is deployed at the border of a Voice Over Internet Protocol (VoIP) network and protects the network by policing media (or ‘communication’) sessions such as voice calls (or ‘VoIP calls’) flowing into or out of that network. An SBC may have to relay media data for a media session, for example, either because the media data transits the protected network and needs policing, or because the originating and terminating endpoint devices for the media session cannot send media data to each other directly as they are located in different private networks.
Media sessions such as voice calls are commonly set up using the Session Initiation Protocol (SIP). Media sessions generally involve transfer of media data via a media path and transfer of signaling (or ‘control’) data via a signaling path. A SIP session involves an offer stage and an answer stage.
The offer stage involves one or more offer messages encapsulated or embedded in one or more SIP signaling messages being transmitted from an originating endpoint device to a terminating endpoint device. Offer messages typically carry a description of the media parameters for the media session, including a network address associated with the originating endpoint device to which media data from the request receiving device should be transmitted. An offer message may for example take the form of a media session setup request, a media session modification request or a media session deletion request. Offer messages frequently traverse a number of SBCs en-route and typical behavior of each SBC device is to re-write a network address contained in the offer message with a local network address before forwarding the offer message.
The answer stage involves one or more answer messages encapsulated or embedded in one or more SIP signaling messages being transmitted in the opposite direction to the offer messages, i.e. from the terminating endpoint device to the originating endpoint device, in order to accept or reject the communication offer. Answer messages typically carry a description of the media parameters for the media session, including a network address associated with the terminating endpoint device to which media data from the answer receiving device should be transmitted. An answer message may for example take the form of a media session setup response, a media session modification response or a media session deletion response. Answer messages frequently traverse a number of SBCs en-route and typical behavior of each SBC device is to re-write a network address contained in the answer message with a local network address before forwarding the answer message.
The term “network address” is used generically in this document to cover both the internet layer address (source and destination IP address) and transport layer address (source and destination port). Interactive Connectivity Establishment (ICE) functionality is an extension to SIP and is described in Request for Comments (RFC) 5245 of the Internet Engineering Task Force (IETF) network working group. It allows the offer messages to carry one or more network addresses associated with the originating endpoint device to which media data from the terminating endpoint can be transmitted. In ICE, the answer messages also carry one or more network addresses associated with the terminating endpoint device to which media data from the originating endpoint can be transmitted. Following receipt of the answer message by the originating endpoint device, the network addresses associated with the originating endpoint device and terminating endpoint device are paired, with each network address associated with the originating endpoint device being paired with each network address associated with the terminating endpoint device. One pair is selected for use in the media session.
The originating endpoint and terminating endpoint will only apply ICE procedures if no other device has interposed itself in the media path. If a device has interposed itself in the media path, the terminating endpoint identifies this, and acts as if ICE functionality was not present. This presents a problem for an SBC processing an ICE offer message because if the SBC follows typical behavior and interposes itself in the media path, then ICE functionality is no longer available for the media session.
It would therefore be desirable to provide improved methods for controlling establishment of media paths for media sessions in a telecommunications network, including in the presence of ICE enabled endpoints.